This invention concerns apparatus for monitoring the output of an electrical indicator of rotation for detection of malfunctions. Such rotation transducers are utilized for control functions in engines.
It is known for conversion of rotary movements into an electrical signal to use a so-called rotation transducer. These rotation transducers deliver an analog output signal the value and, if appropriate, the sign of which are a measure for the angular position of a rotary part of which the movement is to be converted into an electrical voltage. To the extent that it is important to determine the angular position with reference to a particular zero-position absolutely, serious malfunction can occur when the rotation transducer is mismounted on the rotary part or shifts its position during operation as the result of a mechanical loading of the rotary part. In such cases, the output signal value, which is supposed to designate the angular position of the rotary part, no longer corresponds with this angular position, with the result that regulating or controlling devices responsive to the output signals that are intended to be controlled by the rotation transducer fall into malfunction.
A field of application for such rotation angle transducers is the determination of the angular position of a crankshaft of an internal combustion engine, for example a Diesel engine. In this case, precise information of the absolute angular position of the crankshaft relative to a reference mark is necessary for the correct determination of the moment of fuel injection. The reference mark may, for example, be the upper deadpoint of the cylinder in question. If the rotation transducer shifts during operation, as the result of a mechanical loading, the fuel injection control of the Diesel engine is provided by signals offset by the shift angle and damage to the Diesel engine can result. For this reason, there is a need for monitoring the output signals of such a rotation transducer with respect to the accuracy of the correspondence of the output signal to the angular position of a rotary part. Furthermore, it is necessary in such devices to recognize a possible failure of the rotary transducer in order to provide the necessary transition in such a case to an operationally safe condition of the installation or vehicle.